Rhodamine 6g & 532nm

[jonsinger]

@LesioQ --

Hi.

(I was the one asking for CR-599 mirrors, actually. Steve was quoting me in his response.)

I found a PDF about this model, and it has part #s in it --

The pump mirror part # is 406-721-xx, where xx is either 01, 02, or 03. (For most dyes you would use 406-721-01.)

Fold mirror part #s all seem to be 0158-788-xx, where xx is some number between 02 and 11.

MaxRef mirror part #s are the same except that they are 0158-787-xx; the last 2 digits are the same as the ones on the fold mirror for any given dye. For example, for R6G, the fold mirrors is 0158-788-07, and the HR is 0158-787-07.

The OC for R6G is 500-836-03 (also works for R110); but the numbers for other dyes are quite variable. Two of them begin with 155-, three of them begin with 157-, and five of them begin with 500-.

(Info from http://192.197.62.35/courses/phtn140...tProcedure.pdf )

My bet is that "787-07A" is a MaxRef mirror for R6G, and the smaller one is a pump mirror that would work for R6G. I don't know for sure whether a 787 can be used in place of a 788, but my initial guess is that they are probably interchangeable.

I suspect that I'm interested in these...

Best --
jon

[jonsinger]

So, I found an article that I think I mentioned, possibly in my first posting. It is from Sov. J. Quantum Electron., v9n9 (September, 1979), pages 1191-1193, and it is by Knyazev, Lebedev, and Fokin. The title is "Photochemical effects in a high-power flashlamp-pumped laser utilizing solutions of Rhodamine 6G in isopropyl alcohol". If you are interested in this issue & have access to a University physics library it is probably worth reading.

I can't quote the entire thing, but for their main laser they were putting 10kJ into their lamps, which were loosely coupled to a rectangular dye cell 250 mm long, 90 mm high, and 4 mm thick. The pump pulse appears to me to have been slightly overdamped; they state that it had risetime of 15 microseconds and FWHM of 70 microseconds.

What they found, basically, was that if they used ethanol as the solvent, the output went down by about half every time they fired the lamps; it was somewhat better if they ran the solution through an Al2O3 filter (slowly -- if they pushed it, the filtration didn't help). If they used isopropanol, it wasn't quite as bad. "But wait! There's more!" --

They also tried putting plain glass between the lamps and the dye cell, to cut the really short UV. Their rationale was that this eliminated absorption of pump light by the solvent, leaving the longer UV and the visible to pump the R6G into its S1 and S2 states. With ethanol, it helped, but not all that much; with isopropanol the output actually went _up_ for the first few pulses, and didn't get down to 50% of the initial value until after ~12 to 16 pulses.

This suggests that you could use a plain glass or borosilicate tube for a little (or even big) lamp-pumped R6G laser. It also suggests that 91% iso from the drugstore (which is what I typically use anyway) is likely to be a good solvent.

Cheers --
jon

[planters]

Thanks for the reference. I was able ( mixedgas thanks for the recommendation) to talk at length to the engineer at Exciton ( I promise to buy all dye laser supplies from them. He was VERY helpful). For RG6 the recommended mix for flash lamp driven lasers centers around 5.5x10-5 in 50:50 methanol: water( methanol works fine but the water inhibits flammability).Ammonyx should be added at 2-4% to increase the fluorescence yield. The higher concentration should used with higher water ratios. The titration method was repeated, but with a twist. Set the flash lamp to 90% output and add dye concentrate until the near field just changes from a disk to an annulus then increase the flash lamp to 100% and you will be set. Basically, COT will be beneficial for any laser pulse longer than 300-400nsec; due to triplet state accumulation. Also, the COT acts to increase the stability of the dye mix (improve its’ longevity) and the COT is added from 10x to 100x the concentration of the dye, with laser output at first increasing as the COT is added and then as it continues to be added the output starts to decline. COT is deactivated over time by contact with oxygen and has to be replenished.
The recommendation is that we should avoid UV was repeated and so a Pyrex flow tube is definitely a go ( on order).

[LesioQ]

Maybe a Samarium doped glass tube is a way to go without UV

Piotr.K

[planters]

Effeciency wise, probably. But, cost wise not.
Also another question. Iif I am interested in a source of quasi- continuous orange/yellow ( I have a pretty good 640nm red) are the mirrors in a LS dye head broad band enough to allow operation of an RG6 dye mix at 590nm -600nm? Also is the output from a LS KTP polarized? Is the output from the dye head polarized?

[dsli_jon]

Hey Sir E -

Also another question....are the mirrors in a LS dye head broad band enough to allow operation of an RG6 dye mix at 590nm -600nm?

Should-be, but it will be a question of 'how much'.. Also, #1, have a look at this curve of a 'cousin' of the mix that is in the LS 600s..



..the 600s use Sulforhodamine 640, which obviously is tailored to peak between 629 - 640, but clearly, SR can produce lines well-into orange / close to yellow.
#2, I've actually tried mixing some R6G in-with the native LS-mix, and I've *definitely* seen some lower-than 629-lines - one, very-close to 600, for-sure...very yellow-dominant, clear distinction from the oranges you can pluck-out with a BRF... not sure about as low-as 590, but I'd opin that at least in my 'rough-tests', that might be more a function of this particular R6G-mix, vs the optics...

Also is the output from a LS KTP polarized? Is the output from the dye head polarized?

Randomly, but you can 'shift' with a 1/4 wave-plate (one on every LS-532 deck...) / mirrors... Curious, what's the application for pol'd 532?

ttyl..
j

[planters]

For the best efficiency from 590-600nm I assume RG6 would be the best choice for the dye even if there is some coverage by SR, but I may be wrong. What would be the relative performance of these two dyes? I'm not very familiar with the dye head, however I assume that if the HR and OC were optimized for the chosen wavelength then the other optics would be relatively forgiving and allow efficient lasing. It would be nice not to have to replace any optics, but a couple of straightforward mirrors may not be too bad.
I have access to a couple of high quality pol BSCs and plan to use any Q switched 532 output to drive dye heads. So, this was just to learn if the system would allow these PBSs to would work and it sounds like it would.

[mixedgas]

Why dont we get the first design paper on the ring dye laser, and one of Hansch's first papers for the pulse pumped dye and settle all this by getting the first testing data?

H.W. Kogelnik, E.P. Ippen, A. Dienes and C.V. Shank, Astigmatically compensated cavities for cw dye lasers, IEEE J Quant Electr QE-8 (1972), pp. 373–379.

Would love a copy if some one can get it...

We possibly want the papers referenced in the paper as well.

Steve

[krazer]

That paper does not have any useful numbers about different dyes, it just talks about (surprisingly enough) compensating for astigmatisms due to the dye cell/folding mirror being at funky angles.

One of the references 'High-Efficiency Tunable CW Dye Laser' has some nice numbers:
*used a brewster prism for pumping and wavelength selection
*used the 3 mirror design with some astigmatism compensation
*3.5W CW pump power, 1W output power at 590nm using a 5% oc
*noted 5% oc was not optimal, further efficiency gains possible
*used 4e-4 molar RG6 in water, with 4 percent Amonyx LO
*further power gains were possible with .05 percent cyclooctatetraene(COT), but the dye quickly degraded

[mixedgas]

The reason for posting that citation is nearly everybody used Kogelnik's three mirror design, and its referenced in that paper.
I knew the dye gains would not be there. I hoped the cited references would be closer to what we are looking for.
That paper was cited at the back of two dye laser service manuals, from two different manufacturers.

You found what we were looking for, so the idea worked.

Steve